1. Field of the Invention
The present invention relates generally to mechanical locks, and more particularly, to "shell and core assemblies" that have a cylindrical shell mountable on a wall of an enclosure and a removable core.
2. Description of the Background Art
A variety of mechanical locks are known, including locks to secure dwellings, buildings, vehicles, compartments, access hatches, gates, etc. Mechanical locks typically have a rotatable plug containing a key slot. The insertion of a correctly-bitted key displaces tumbler pins within the plug, thereby allowing the plug to rotate. The rotation of the plug actuates a locking bolt or the like that locks or unlocks the structure that the lock is a part of. If the key is not a correctly-bitted key, either the key will not be able to fully enter the slot, or the lock will not be allowed to rotate. "Shell and core" lock assemblies are known wherein the lock components include separate "cylindrical shells" and "cores" that can "together" be installed in a wall of an enclosure, transported by a manufacturer, and removed from the enclosure for replacement. "Shell and core" lock assemblies have also been enhanced by the provision of "removability" of the "core" from the "shell" by the use of a special key, to facilitate lock replacement. In a removable core lock, the plug, including the key slot and tumbler pins, can be removed from the lock while leaving the remaining lock mechanism in place. A removable core lock offers the advantage of being able to easily and cheaply change the keying of the lock without removing and replacing all of the lock apparatus. Removable core locks may be commonly used in applications such as casinos, dormitories, hotels or motels, lockers, rental units, or other applications where re-keying of locks is anticipated. The advantages include not only a lesser cost in hardware replacement, but also significant time and labor savings.
These removable core locks have suffered from several drawbacks. First, these removable core locks have commonly contained a complicated structure, e.g., with the cores being retained in the shell by a tumbler pin or another movable internal retaining device. When the core is removed from such locks, these retaining devices have an unfortunate propensity for falling out of the lock or becoming unseated from a desired position. Second, such removable cores can be difficult to install and remove.
An old device outside of the context of a "shell and core" assembly (i.e., having a core that is alone removable from an automobile handle) is shown in U.S. Pat. No. 2,036,764 to Lowe. In Lowe, the removable core is retained inside the handle via two thin L-shaped arms extended from the plug. The Lowe device has several drawbacks. First, the device does not relate to a transportable and/or removable "shell and core" assembly. Second, each L-shaped arm has a lower level of strength and durability. Third, the L-shaped arms can be hard to align if the L-shaped arms 24 become twisted or bent during handling of the plug.
What is needed is a "shell and core" lock assembly that can be sold and delivered as a unit by a manufacturer for incorporation in enclosures, wherein the core can be easily and efficiently removed and replaced without problems of existing removable core devices and with increased strength and durability.